Maintenance of Methyl-Esterified Pectin Level in Pollen Mother-Cell Stages Is Required for Microspore Development

Pectin modification and degradation are vital for plant development, although the underlying mechanisms are still not well understood. Furthermore, reports on the function of pectin in early pollen development are limited. We generated OsPME-FOX rice lines with little methyl-esterified pectin even in the early-pollen mother-cell stage due to overexpression of the gene encoding pectin-methylesterase. Overexpression of OsPME1 in rice increased the activity of PME, which decreased the degree of pectin methyl esterification in the cell wall. OsPME1-FOX grew normally and showed abnormal phenotypes in anther and pollen development, especially in terms of the pollen mother-cell stage. In addition, we examined modifications of cell-wall polysaccharides at the cellular level using antibodies against polysaccharides. Immunohistochemical staining using LM19 and LM20 showed that methyl-esterified pectin distribution and the pectin contents in pollen mother-cell wall decreased in OsPME1-FOX compared with the wild type. Thus, the maintenance of methyl-esterified pectin plays a role in degrading and maintaining the pollen mother-cell wall during microspore development.

Automated summary

Pectin modification and degradation are crucial for plant development, but the mechanisms behind it are not well understood. This study explored the function of pectin in early pollen development. By overexpressing the OsPME1 gene, which encodes pectin methylesterase, rice lines with reduced pectin methyl esterification were generated. These lines showed abnormal phenotypes in anther and pollen development, especially in the pollen mother-cell stage.